Hello,
I checked the links... TAW XtreamScreen is expensive as it is made of special material which is said to be children proof
It has a gain of 6.0, but I doubt that is the reason why it is expensive as well as I doubt such a screen could be used in a dedicated HT at all unless you will be wearing very dark sunglasses.
What indicates it is the material of the screen that makes for the higher price is when there is an increase in size, price rises strongly...